This invention relates generally to the sealing of fittings about tubes and more particularly, though not exclusively, to the sealing of tubing using a single tube gripping member, such as a ferrule.
Tube fittings are used to join or connect a tube end to another member, whether that other member be another tube end or a device in fluid communication with the tube end. Generally, tube fittings are designed to withstand operational conditions of the environment where the tube is located, such as pressure, vacuum, pull-out pressure, temperature, pulsation and/or vibration. Ideally, a tube fitting grips the tube end so as to prevent loss of seal between the tube and another member. A good tube fitting maintains a leak-free connection between the tube and another member.
Some tube fittings are designed to be used with plastic tubes, while others—with metal tubing, such as stainless steel pipes/tubes. While the design criteria for these applications may differ, the basic concepts of this invention may be applicable to both. Typically, stainless steel and other metal tubing is used for high pressure applications in which the tubing wall thickness is substantial. Such heavy wall tubing is difficult to grip because it is not only hard but it is also resistive to deformation. Such physical characteristics make it more difficult to deform the tubing plastically so as to achieve a desired tube grip.
Tube fittings usually include an assembly of a tube gripping device, which can be a single or double ferrule, and a pull-up member for causing the tube gripping device to be installed on a tube end so as to grip the tube end and create a leak-free seal. The pull-up member can be a threaded nut that is tightly engaged with the body of a member, to which the tubing is connected. The pull up mechanism most commonly used is a threaded connection of a female threaded nut and a male threaded body component, both of which act upon the ferrule as the nut and the body are threaded together. In such arrangement, the front end of the ferrule is sandwiched between the tube and the body to form a sealing member.
Conventional single ferrule fittings are inserted into a space between an outer surface of the tubing and an inner surface of the body. The body is formed with a frustoconical camming surface, which a front end of the ferrule contacts. In many known fitting assemblies, the resulting seal is less than adequate, requiring one or more elastomeric seals to prevent leakage of the liquid or gas.
The present invention contemplates elimination of drawbacks associated with convention tube fitting and provision of a single ferrule seal assembly that effectively seals the interface between the end of the tubing and a body.